Truck tractor



FIG. 1 is a perspective view of a truck tractor, showing my new design;

FIG. 2 is a top plan view thereof on a reduced scale;

FIG. 3 is a right side elevation view thereof on a reduced scale;

FIG. 4 is a back elevation view thereof on a reduced scale;

FIG. 5 is a front elevation view thereof on a reduced scale; and,

FIG. 6 is a left side elevation view thereof on a reduced scale.

The ornamental design for a truck tractor, as shown.